Controlling means for single-phase motors.



No. 847,172. PATENTED MAR. 12, 1907.

' A. R. EVEREST.

CONTROLLING MEANS FOR SINGLE PHASE MOTORS.

APILIOATION FILED JUNE 22,1905.

Fig.1 R I Wimmses inven for 5/ I Augusrme Riven-25+ l l N ITED' STATES PATENT OFFICE. AUGUSTINE R. EVEREST, Or iiNN, fissiionusnrrs, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

CONTROLLING MEANS FOR SINGLE-PHASE MOTORS.

Specification of Letters Patent.

Patented March 12, 1907.

Application filed June 22, 1905. Serial N0. Z66,431.

To all whom, it may concern:

Be it known that I, AUGUSTINE It. EVER- EST, a subject of the King of Great Britain, residing at Lynn, county of Essex, State of Massachusetts, have invented certain new and useful Improvements in ontrolling Means for Single-Phase Motors, 0 which-the following is a specification.

My invention relates to the control of single-phase motors of the induction type. As is well known, such motors will not start from rest unless special starting devices are'employed, such as an auxiliary starting-windmg or a phase-splitting device connected in the motor-circuit, or both. Ordinarily such starting devices are designed for operation for only a short time and if left too long in circuit with the motor would become overheated. Moreover, when the motor is up to speed the efficiency is generally better if the starting devices are cut out of circuit.

The object of my invention is to provide automatic means for cutting the starting devices out of circuit when 'the motoris up to speed, and for this purpose I make use of the fact that the motor-current at starting is much greater than when the motor is up to speed.

My invention accordingly consists in the combination, with a single-phase inductionmotor having diiferent connections for starting and running, of a switch arranged to connect the motor for starting or for running and a magnet-winding connected in the motor-circuit and controllin the switch.

More s ecifically stated, my invention consists in tlie combination, with an inductionmotor of the type employing a three-phase winding, with two of the terminals connected to the single-phase source, and with two devices of different impedance factors connected in series with each other and in shunt to the motor and connected from a point between said devices to the third terminal of the motor, of a magnet-winding inserted in said connection and controlling a switch arranged to break the circuit of said devices when the motor is up to speed. This connection of the magnet has s ecial advantages, since the current througli the magnet, while large at the start, falls practically to zero as the motor comes up to speed, and consequently the action of the magnet upon the switch may be made very positive.

My invention further contemplates the combination, with a motor of the type described above, of a switch arranged to con-- nect the motor for starting or for running, means for locking the switch in starting position, a magnet in circuit with the motor controlling the locking means, and means for antomatically moving the switch to running position when released by the locking means.

My invention further comprises a switch having certain structural features which adapt it for use in the combinations set forth above.

My invention will best be understood by reference to the accompanying drawings, in

' which Figure 1 shows diagrammatically asinglephase induction-motor provided with controlling means arranged in accordance with my invention, and Fig. 2 shows the construction of the controlling-switch.

In Fig. l, A represents the primary winding of themotor, which is shown as a threephase winding delta-connected. B represents the rotor, which may be of the usual squirrel-cage type. Two of the motor-terminals are connected to the source of current a through a switch S. R and I represent, respectively, a resistance and inductance which are connected in series with each other and which may be connected in shunt to the motor by the switch S. The point of connection between the resistance and inductance is connected to the third terminal of the motor, and a magnet-winding M of low impedance is inserted in this connection. The switch S, in addition to the contacts connected to the source, is provided with two sets of contacts 0 and c, which roject outwardly from the switch-base and are of different lengths. These contacts are connected to the motorterminals and to the terminals of the starting devices, respectively.

The operation is then as follows: At starting, the switch S is moved manually to its extreme closed position, in which it enga es not only the lon er set of contacts 0, but a so the shorter set 0 contacts a In this position two of the motor-terminals are connected to the source, and the phase-splitting devices R and I are connected in shunt to the motor.

The point between the resistance and induct- .ance is connected to the third terminal of the winding M.

in the usual manner. and a current of considmoved auton'iatically outward l rom engage- -n1ent with the shorter contacts 0 into the position shown. ing devices are cut out ol circuit while the motor is still connected to the source.

The fall of current through the magnet- This current is utilized, as will I r\t this point, or a little bel'orc. the i switch S is released b v.the magnet M and is The motor consequently starts the switch breaks the circuit otthe starting device in the manner herctol'orc explained.

Many changes may he made in the arrangement ot the start mg devices and ol the switch. For instance,it. is essential only that In this position the start- 5 winding M as the motor speeds up is due to t the following causes: It is well known in the art that a single-phase induction-motor at starting has simply a pulsating unidirectional field due to the single-phase current supplied thereto, while when the motor is up to speed a rotary field exists in the motor or, in other words, the rotation of the secondary member produces a cross-magnetization which induces in the motor-windings an electromotive force in quadrature with the impressed electromotivc force. Conseuently in the arrangement shown in Fig. 1

t to magnet-winding M at starting has impressed upon it the voltage due only to the phase-splitting devices. As the motor speeds up the crossmagnetization rises, inducing an electrornotive force in the primary winding of the motor in quadrature to the impressed electromotive force and counter to the electromotive force produced by the phase-splitting devices. Consequently as this counter electromotive force increases the current through the magnet-winding M falls.

A suitable construction for the switch S is shown in Fig. 2. In this figure the switchblade is shown in full lines in its extreme closed positionthat is, in the starting position. A plunger D, movable perpendicularly with respect to the switch-base, engages the 0 switch S and is provided with a compressionspring (I, which tends to move the switch from its extreme closed position. The armature m of magnet-winding M is provided with a locking device L, which when the armature m is drawn up, as shown in Fig. 2, engages the plunger D and looks it in the position shown. t'hen, however, the current in magnet-wind- 1 ing M falls t a predetermined amount, the armature, falls by gravity or by means ol a tension spring m, lowering the locking (leviceL out ot engagement with the plunger I). The lunger is consequently moved outwardly by the compression-spring d and pushes the switch-blade S into the position shown in dotted lines.

This movement of the starting devices shall have dill'crcut impedance factors, and consequently a condenser might be substituted for either the resistance or the inductance. ()ther motor connections may be employed, and the st ructure and arrangement ol" the controllingswitch may be altered as desired. Accordingly I do not desire to limit mysell' to the particular construction and arrangement ol parts here shown, but aim in the appended claims to covc' all modilicatious which are within the scope ol my invention.

What I claim as new, and desire to secure hyfLetters Patent 01' the L nited States, is-

1. In ctnnbiinition with a single-' 'diase induction-motor, phase-splitting devices for starting said motor, a switch arranged to cut said devices out ol circuit, and a magnetwinding connected in circuit with the motor and controlling said switch 2. In combination with a single-phase induction-motor having dill'erent connections for starting and for running, a device controlling said connections and responsive to variations in the component ol' the eltttnw motive force induced in thc motorwiiulings in quadrature with the impressed (ltttl'omotive force.

In combination with a single-phase induction-motor, a phasesplitting starting device, and means for breaking the circuit of said device responsive to variations in the component of the electromotive force induced in the motor-windings in quadrature with the impressed electromotivc lorce.

4. In combination with a single-phase induction-motor, a phase-split ting starting device, and means for automatically breaking the circuit of said device when the cross lield produced in said motor by the secondary currents exceeds a predetermined value.

5. In combination with a single-phase induction-motor, having main circuit. connections for running and dill'erent connections for starting, a switch adapted to change said connections from starting to running conditions, and a magnet controlling the said switch connected in quadrature to the main i circuit connections.

source, two devices of ditl'erent impedance iltt factors connected in series with each other 1 to break the circuit of said devices when said and in shunt to the motor, a connection from I a point between said devices to the third 1110-. tor-terminal, a magnet-winding in said 0011- nection, and a switch controlled by said magnet-winding and arranged to cut said (10- vices out of circuit.

""8 In combination with an induction-motor having diil'erent circuit connections for starting and running, a switch arranged to establish starting connections in one of its positions and running connections in another, a magnet-winding in circuit with said motor, means controlled by said magnet-winding for locking the switch in its first position, and means for moving said switch automatically to its other position when released by said locking means.

9. In combination with a single-phase induction-motor, phase-splitting devices for starting said motor, a switch arranged in one -position to connect said devices in circuit with said motor and in another position to cut them out of circuit, a magnet-winding connected in circuit with said motor, means controlled by said magnet-winding for locking saidswitch in the first position, and means for movingsaid switch automatically to its other position when released by said locking me ans.

10. In combination with an induction-mo-- tor having a three-phase Winding with two of its terminals connected to a single-phase source, two devices of different impedance factors connected in series with each other and in shunt to the motor, a connection from a point between said devices to the third motor-terminal, a magnet-winding in said con nection, a switch in series with said devices, means controlled by said magnet-winding for looking said switch in closed position, and means for moving said switch automatically switch is released by said locking means.

11. In combination with a single-phase induction-moton starting devices therefor, a switch-base, a knife-blade switch pivoted on said base and movable in aplane at right angles to said base, two sets of contacts of different lengths extending outwardly from said base the longer set being connected to the primary winding of the motor and the shorter set to the starting devices, and means for moving said switch automatically out of engagement with the shorter set of contacts.

12. In combination with a single-phase induction-motor, starting devices therefor, a switch-base, a knife-blade switch pivoted on said base and movable in a plane at right angles to said base, two sets of contacts of different lengths extending outwardly from said base, the longer set being connected to the primary winding of the motor and the shorter set to the starting devices, and a spring-operated plunger adaptedto move said switch out of engagement with the shorter set of contacts.

13. In combination with a singlephase induction-motor, phase-splitting devices for starting said motor, a switchmanually mov able to connect said motor to the source and to connect said phase-splitting devices to the motor, automatic means for moving said switch to out said devices out of circuit, and

a magnet-winding in circuit with said motor and controlling said switch.

In witness whereof I have hereunto set my hand this 20th day of June, 1905.

AUGUSTINE R. EVEREST Witnesses: V

JOHN A. MoMANUs, Jr.. HENRY O. WEsTENDARr. 

